Speed control, or cruise control, systems keep the speed of the vehicle at a level set by the driver without the driver having to maintain pressure on the gas pedal. The driver can then cruise at a fixed speed without continually checking the speedometer.
The driver brings the vehicle up to a desired speed and turns on the cruise control. The driver then programs that speed into the system by pressing a button. An electronic sensor measures the speed at which the vehicle is traveling. A computing device differentiates between the information it receives about the actual speed and the desired speed that the driver programmed into it. The computer then sends a signal to a servo to set the throttle so that the torque generated by the engine is at the level needed to have the vehicle travel at the desired speed.
A problem with current speed control systems, however, is that the driver may perceive a deviation between the speed of the vehicle via the speedometer and the desired speed. This is due to the fact that the vehicle speed sensed by the electronic sensor is filtered via a filter that has a fast response as requested by the vehicle speed controller, while the speedometer has a slow response to the speed change. It is difficult to design a filter to compromise between the two different requirements on response time.